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How do you test a sump pump?

Updated August 2026

15 minutes · Easy DIY

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Pour a 5-gallon bucket of water into the pit and watch the entire cycle: the float rises, the pump starts, the pit empties in 10 to 20 seconds, and the switch shuts off cleanly. That is the only test that proves the pump can move water, and it takes 15 minutes. Do it every 3 to 4 months, and always before a wet season or a long trip. The pump that fails at 2 a.m. during a storm is almost always the one that has sat idle since last spring.

What you need

Before you start: A plugged-in motor and standing water share the same hole in your floor, so treat the pit carefully. Unplug the pump before reaching in to clear debris or reposition a float, and never lift the pump by its cord. The receptacle feeding it should be GFCI protected; if it is not, that is a $150 to $250 electrician fix worth scheduling. Stop and call an electrician if the outlet is damp, the cord is cracked, or the pump has ever been submerged above its motor housing.

Steps

  1. Lift the pit lid and look before you pour anything. Gravel, silt, and shreds of insulation collect around the pump intake, and a screen packed with sludge chokes capacity long before the motor fails.
  2. Confirm the pump is plugged into a GFCI outlet and that a piggyback float plug is fully seated with the pump plug in the back of it. A half-seated stack is a common no-start.
  3. Pour the 5 gallons in slowly down the pit wall so the float is not slammed sideways. Note where the float sits when the motor kicks on; it should trip well below the level of the basement floor.
  4. Time the run. A working 1/3 hp pump clears a typical pit in 10 to 20 seconds and then shuts off without stuttering back on two or three times.
  5. Listen for one solid clunk after shutoff. That is the check valve closing. Repeated restarts mean water in the vertical pipe is draining back into the pit and a $15 to $30 check valve is leaking.
  6. Walk outside and confirm water is leaving the discharge and running at least 10 feet from the foundation, rather than pooling at the wall and soaking straight back into the pit.
  7. Pour a second bucket and confirm the pump repeats the cycle. A single good start can hide a sticking float or a heat-soaked motor.
  8. If you have a battery backup, unplug the primary pump and pour again. The backup should start on its own and the alarm should sound. Backup batteries need swapping every 3 to 5 years; details on how often to replace a sump pump battery backup.

Or hire it out

A plumber charges $100 to $175 to test and service a sump pump on a standalone visit. A new pump is $150 to $500 for the unit, or roughly $400 to $900 supplied and installed.

Done. Now the part everyone skips: doing it again on schedule. Log it in OnOtto and the next reminder for sump pump tests sets itself.

Log this task, get the next reminder

Frequently asked questions

Can I just lift the float instead of pouring water?

Lifting the float only proves the switch works. It says nothing about whether the impeller still moves water, whether the check valve holds, or whether the discharge line is crushed, blocked by a nest, or frozen shut at the exit. Plenty of pumps pass a float test all winter and then run dry against an ice plug in March. Use real water, and follow it outside to the discharge point.

The pump runs but the water level barely drops. Why?

Three suspects, in order. First, a clogged impeller: silt and pea gravel get sucked in and pack the housing. Second, a blocked or frozen discharge line, which you can hear as a straining motor with no flow outside. Third, an airlock, which happens when the small weep hole in the discharge pipe plugs up. Clear the pit and the intake first, since that is free and fixes most cases; timing is on how often to clean a sump pit.

How often should I test it, and when is the pump worn out?

Test every 3 to 4 months, plus once right before your wet season and once before any trip longer than a weekend. Clean the pit annually. Most pumps run 7 to 10 years, and closer to 5 in a house where the pump cycles daily from a high water table. Age plus a slow start or a rattling motor is your cue to replace it before the next storm rather than during it. See how often to replace a sump pump and how long a sump pump lasts.

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